spike(embedded-mpv): scope macOS frame-copy engine to Apple Silicon only

Owner decision 2026-07-10: skip Intel Mac measurements and gate the future
frame-copy engine on arm64. Intel Macs able to run the app at all are a
shrinking 2015-2020 cohort and keep the docked/external/web player paths;
the macOS hardware gate closes with the M1 Pro numbers, and remaining
hardware risk moves to the Windows/Linux ports.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

spikes/mpv-frame-copy/DESIGN.md

@@ -97,6 +97,14 @@ scope for v1.
 - Windows shm: POSIX `shm_open` on macOS/Linux, `CreateFileMapping` named
   sections on Windows behind the same header layout.
 
+## Platform scope
+
+macOS: **Apple Silicon (arm64) only** — owner decision 2026-07-10. Support
+detection gates on the CPU architecture; Intel Macs keep the existing
+docked native path, external players, and web engines. This closes the
+macOS hardware gate with the M1 Pro measurements and moves all remaining
+hardware risk to Windows/Linux.
+
 ## Platform bring-up order
 
 1. macOS: spike is the implementation seed (CGL headless + PBO ring).
@@ -117,8 +125,8 @@ scope for v1.
 
 ## Open gates before default-ON
 
-- Intel Mac / Windows iGPU numbers (pending hardware; RESULTS.md has the
-  repro recipe).
+- Windows iGPU numbers (needs the Windows helper port; RESULTS.md has the
+  repro recipe). Intel Mac gate closed by the arm64-only scope decision.
 - Latency flash test + per-platform `--audio-delay` calibration.
 - Battery drain delta vs the native-surface approach.
 - Windows/Linux helper ports validated on real machines.

spikes/mpv-frame-copy/README.md

@@ -100,8 +100,9 @@ Measured on M1 Pro (2026-07-10):
 
 Still open:
 
-- Intel Mac and mid-range Windows laptop (iGPU) — the actual risk hardware
-  (pending device; Windows also needs the helper port).
+- Mid-range Windows laptop (iGPU) — the actual risk hardware; needs the
+  Windows helper port first. (Intel Macs: skipped by decision — on macOS
+  the engine targets Apple Silicon only, see RESULTS.md.)
 - End-to-end latency flash test (photodiode/screen-capture method) and
   audio/video sync offset to calibrate `--audio-delay`.
 - Battery drain delta vs the native-surface approach.

spikes/mpv-frame-copy/RESULTS.md

@@ -96,10 +96,16 @@ Reference worst-case budget from the analysis doc, for orientation:
 33 MB 4K memcpy est. 6–8 ms (measured ≈1.2 ms); end-to-end added latency
 est. 40–60 ms (measured ≈10 ms produce→uploaded, before compositor).
 
-## Intel Mac — PENDING (device to be sourced)
+## Intel Mac — SKIPPED by decision (2026-07-10)
 
-Target scenarios: same three rows as above (hwdec=videotoolbox on Intel
-iGPU is the interesting case) + windowed vs fullscreen.
+Owner decision: the frame-copy engine targets Apple Silicon (M1+) only on
+macOS; support detection must gate on arm64. Rationale: Intel Macs able to
+run the app at all (Electron 41 ⇒ macOS 10.15+) are a shrinking 2015–2020
+cohort and keep the existing docked/external/web player paths; the only
+Intel device sourced (iMac mid-2011, High Sierra) cannot run the app and
+would not have been representative. The macOS hardware gate is therefore
+closed by the M1 Pro numbers above; the remaining risk hardware is
+Windows/Linux.
 
 ## Windows mid-range laptop (iGPU) — PENDING